Improve samples (e.g. for Objective) in Web API

[xsebek]

The Web API documentation can automatically generate example queries and results using the ToSample instance.

Add this instance to all used types, namely:

• Objective which is transitively required by
  • GoalTracking
  • WinCondition

It would be good to read the Servant docs and make it look good and readable.

Leftover from:

• Web API docs improvements #1529

[xsebek]

An example from swarm generate endpoints:

---

GET /repl/history/full

Response:

• Status code 200

• Headers: []

• Supported content types are:

  • application/json;charset=utf-8
  • application/json

• Example (application/json;charset=utf-8):

[]

• Example (application/json;charset=utf-8):

[{"in":"grab"}]

---

The ideal would be to have this for all endpoints, so that its easy to test first on dummy data.